This relates generally to electronic devices with displays and, more particularly, to electronic devices with calibrated displays.
Electronic devices such as portable computers, media players, cellular telephones, set-top boxes, and other electronic equipment are often provided with displays for displaying visual information.
Displays are often capable of displaying color images. However, the color response of a display may change as the display operates. For example, changing operating conditions such as changing display temperature may affect the color response of a display. Some displays depict white as somewhat yellowish when initially powered on and cold. As the display warms, the white point of the display shifts toward a more neutral white, such as that defined by the standard illuminant, D65. Other display colors such as skin tone colors may also experience shifts within a color space as the temperature of the display changes. Similarly, other parameters of the display may shift as a function of temperature such as luminance, black level, contrast, or electro-optical transfer function, which may be referred to as the “native gamma” of the display. This set of parameters may be referred to as the color profile of the display.
The shift in the color profile due to temperature changes in the display generally causes each pixel of the display to change color until a stable operating temperature is achieved, at which point the pixel colors may likewise be stable. That is, although a pixel may be instructed to display the same color at an initial temperature and a stable operating temperature, the actual color displayed, as objectively measured by its chromaticity and luminance, may vary.
Displays are sometimes calibrated to account for temperature induced white point shifts. Conventional methods include applying temperature dependent adjustment values to input pixel values to obtain adapted input pixel values. However, the temperature dependent adjustment values are typically optimized for neutral colors such as white. Applying these temperature dependent adjustment values to non-neutral colors leads to an undesirable color shift for the non-neutral colors.
It would therefore be desirable to be able to provide improved ways of calibrating electronic devices with color displays.